Solder ball contact pin is widely used in POL (point of load) DC/DC power regulator applications. A POL DC/DC regulator with the solder ball contact pin provides a SMT compatible solution for mounting a module for final assembly. The pin body (made by copper) provides a rigid, high conductivity connection to a power module (or PCB) and the solder ball onto the contact pin can provide co-planarity compensation when assembling the power module to a host board during the reflow or vapor phase process.
A typical solder ball contact pin includes a solder ball or sphere, an insulator which provides a positive location of the solder ball during the reflow process, and a copper alloy pin body to provide robust connection between the power module and the host board.
In the current existing solution, an insulator surrounding the pin body and adjacent to the solder ball is used as a solder ball contact structure. The insulator mentioned means solder insulator which could be made of an electrical isolated material like FR4 or resin (which is described in patent U.S. Pat. No. 6,700,079). Alternatively, an electrical conductive material as mentioned in U.S. Pat. No. 7,537,498 is provided to substitute for the insulator to provide a similar function during the reflow process.
Both above solutions include a discrete solder insulator. The assemble process for insulator is complex during the manufacturing, meanwhile due to the solder insulator, it's not good for a solder joint quality when mounting power modules to the host board by means of the solder ball onto the pin body.
Besides that, a test solution for high current solder ball contact POL (POL means Point of load, a DC/DC regulator) becomes a challenge. Usually a test probe pin will move from vertical direction and touch the solder ball. If an electrical current is very high, the test process will generate huge heat due to high contact resistance between the test probe pin and the solder ball. The solder ball can re-melt if the test current is high enough. This will lead to test failure of POL product.
High current POL is the trend for power module industry, but the current solder ball contact solution can't meet the requirement for high current POL manufacture and electrical test process.